The upper frequently hypercyclic vectors of a continuous linear operator always form a Gδσ set, and an explicit weighted shift shows they need not form a Gδ set.
Topological complexity of ideal limit points
1 Pith paper cite this work. Polarity classification is still indexing.
abstract
Given an ideal $\mathcal{I}$ on the nonnegative integers $\omega$ and a Polish space $X$, let $\mathscr{L}(\mathcal{I})$ be the family of subsets $S\subseteq X$ such that $S$ is the set of $\mathcal{I}$-limit points of some sequence taking values in $X$. First, we show that $\mathscr{L}(\mathcal{I})$ may attain arbitrarily large Borel complexity. Second, we prove that if $\mathcal{I}$ is a $G_{\delta\sigma}$-ideal then all elements of $\mathscr{L}(\mathcal{I})$ are closed. Third, we show that if $\mathcal{I}$ is a simply coanalytic ideal and $X$ is first countable, then every element of $\mathscr{L}(\mathcal{I})$ is simply analytic. Lastly, we studied certain structural properties and the topological complexity of minimal ideals $\mathcal{I}$ for which $\mathscr{L}(\mathcal{I})$ contains a given set.
fields
math.FA 1years
2025 1verdicts
CONDITIONAL 1representative citing papers
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On the complexity of upper frequently hypercyclic vectors
The upper frequently hypercyclic vectors of a continuous linear operator always form a Gδσ set, and an explicit weighted shift shows they need not form a Gδ set.